Dielectric filter including laterally extending auxiliary through bores

Abstract

A dielectric filter comprising a dielectric ceramic block which has at least two through bores longitudinally extended in parallel with each other each of which is provided with a resonant conductor, and two auxiliary through bores each being laterally extended from the associated through bore to both lateral side surfaces of the dielectric ceramic block and being provided with an inner conductive film on the inner peripheral surface thereof, one end of the inner conductive film in each auxiliary through bore is separated from a shield electrode provided on the outer surface of the dielectric ceramic block so as to form an open circuit end.

I claim: 
     
       1. A dielectric filter comprising: a dielectric ceramic block having a plurality of outer peripheral surfaces, said outer peripheral surfaces including first and second opposed outer end surfaces, first and second opposed outer lateral surfaces, an outer top surface, and an outer bottom surface opposite the top surface;   a shield electrode provided on the first and second outer lateral surfaces, the outer top and bottom surfaces and the second end surface;   a plurality of resonant conductors provided in the dielectric ceramic block and arranged in parallel with respect to each other, each said resonant conductor including a respective through hole extending from the first end surface to the second end surface of the dielectric ceramic block, and   a respective hole inner conductive film which is provided on an inner peripheral surface of each said respective through hole and extending between (a) a first end opened at the first end surface which defines an open circuit end and (b) a second end at the second end surface connected to said shield electrode on the second end surface which defines a short circuit end;     respective input and output coupling electrodes located on one of the outer peripheral surfaces near said open circuit end and positioned to be capacitively coupled with respective first and last ones of said plurality of said resonant conductors; and   first and second auxiliary through bores provided in the dielectric ceramic body, said first and second auxiliary through bores being laterally extended respectively between (a) a respective said through hole associated respectively with the first and last said resonant conductors and (b) respective other ones of said peripheral outer surfaces adjacent to the one outer peripheral surface, said first and second through bores being provided with a bore inner conductive film on a respective inner peripheral surface thereof, with a portion of the bore inner conductive film located at an opening of each auxiliary through bore at the respective other ones of said peripheral outer surfaces being separated from said shield electrode to define an open circuit.   
     
     
       2. A dielectric filter as claimed in claim 1, wherein a distance between a center of the respective said through hole of each of the first and last resonant conductors and the respective first and second lateral surfaces of the dielectric ceramic block is larger than a distance between the center of the respective said through holes of each of the first and last said resonant conductors and the top surface of the dielectric ceramic block. 
     
     
       3. A dielectric filter as claimed in claim 1, wherein each of said auxiliary through bores is positioned near the first end surface of said dielectric ceramic block. 
     
     
       4. A dielectric filter as claimed in claim 1, wherein the outer top surface of the dielectric ceramic block includes an interstage coupling electrode located near the first end surface of the dielectric ceramic block for capacitively coupling the respective said resonant conductors, and wherein each of said input, output and interstage electrodes is separated from said shield electrode. 
     
     
       5. A dielectric filter comprising: a dielectric ceramic block having a plurality of outer peripheral surfaces, said outer peripheral surfaces including first and second opposed outer end surfaces, first and second opposed outer lateral surfaces, an outer top surface, and an outer bottom surface opposite the top surface;   a shield electrode provided on the first and second outer lateral surfaces, the outer top and bottom surfaces and the second end surface;   first, second, and third resonant conductors provided in the dielectric ceramic block and arranged in parallel with respect to each other, each said resonant conductor including a respective through hole extending from the first end surface to the second end surface of the dielectric ceramic block, and   a respective hole inner conductive film which is provided on an inner peripheral surface of each said respective through hole and extending between (a) a first end opened at the first end surface which defines an open circuit end and (b) a second end at the second end surface connected to said shield electrode on the second end surface which defines a short circuit end;     respective input and output coupling electrodes located on the bottom surface near said open circuit end and positioned to be capacitively coupled respectively with said first and third resonant conductors; and   first and second auxiliary through bores provided in the dielectric ceramic body, said first and second auxiliary through bores being laterally extended respectively between (a) a respective said through holes associated respectively with said first and third resonant conductors and (b) a respective first and second lateral surface adjacent to the bottom surface, said first and second through bores being provided with a bore inner conductive film on a respective inner peripheral surface thereof, with a portion of the bore inner conductive film located at an opening of each auxiliary through bore at respective first and second lateral surfaces being separated from said shield electrode to define an open circuit.   
     
     
       6. A dielectric filter as claimed in claim 5, wherein each of said auxiliary through bores is positioned near the first end surface of said dielectric ceramic block. 
     
     
       7. A dielectric filter as claimed in claim 5, wherein a distance between a center of the respective said through hole of each of the first and third resonant conductors and the respective first and second lateral surfaces of the dielectric ceramic block is larger than a distance between the center of the respective said through holes of each of the first and third said resonant conductors and the top surface of the dielectric ceramic block. 
     
     
       8. A dielectric filter as claimed in claim 5, wherein the outer top surface of the dielectric ceramic block includes at least one electrode located near the first end surface of the dielectric ceramic block for capacitively coupling the respective said resonant conductors, and wherein each of said input, output and at least one electrode is separated from said shield electrode.